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Hathaway B I & Underhill A E. The infrared spectra of some transition-metal
perchiorates. J. Chem. Soc. 1961:3091-6.
lUniversity of Hull, Hull, England]
The infrared spectra of some hydrated transition metal perchiorates, some transition
metal perchiorate-methyl cyanide complexes, and anhydrous copper(ll) perchlorate are reported. The spectra are interT
preted in terms of ionic perchlorates, d
symmetry;
monodentate
perchlorato
groups, C ,,, symmetry; and bidentate per3
chlorato groups,
C ,,, symmetry. (The SCI®
indicates that this 2paper has been cited in
over 465 publications since 1961.]
B.). Hathaway
Department of Chemistry
University College
Cork
Ireland
August 4, 1982
“In the early-1950s, polyatomic anions
such as the nitrate and perchlorate anions
were generally considered to display a negligible ability to act as ligands to transition
metal ions, especially in aqueous solution.
By the mid-1950s,
the pioneering work of
1
C.C. Addison (University of Nottingham)
and his students, using liquid dinitrogen
tetroxide as a solvent, had clearly demonstrated the coordinating ability of the
nitrate ion to transition metal ions such as
iron, cobalt, nickel, copper, zinc, and uranium to form not only the anhydrous nitrate,
i.e., Cu(N0 ) , but nitrato complexes, i.e.,
3 2 ) ).Even in these clear coorNO~[Cu(NO
33
dination complexes
the nitrate ion was still
considered to be a weak ligand and coordination of the nitrate ion to a metal ion was
readily broken by dissolution of these hygroscopic nitrato complexes in water. Nevertheless, the final confirmation of the
covalency of the nitrate-metal
bonding was
2
the demonstration of the volatility of
anhydrous copper(ll) nitrate, which could be
sublimed under vacuum at ca. 200°to yield
blue-green crystals on a 10 g scale.
“In the late-1950s, even against this
background of the covalency of the nitrato
metal bond, the perchlorate ion was still
considered to be the classic non-coordinating anion par excellence, and was traditionally used to maintain the ionic strength
of aqueous solutions used in equilibrium
studies of coordination
complexes. But the
3
demonstration of the volatility of anhydrouscopper(ll) perchlorate under vacuum
likewise established the covalent character
of the perchlorato-copper(Il) bond. One effect of the coordination of a perchlorate
group to a metal was that the point group
symmetry of the free anion, Td, would be
lowered to C ,,, in the moriodentate perchlorato group3 and toC v in a bidentate per2
chlorato group. These symmetry
changes in
coordination of the perchlorate group are
then reflected in both the number of infrared active vibrations, and also the energy
at which the vibrations occur. In our infrared paper, those group theoretical predictions were set out and illustrated using the
infrared spectra of a number of transition
metal perchlorate complexes involving
ionic, monodentate, and bidentate perchlorate groups, of which the latter was presumed to occur in anhydrous copper(ll) perchlorate. Consequently, this paper established the use of a readily available physical
technique, infrared spectroscopy, as a valid
tool for the determination of the bonding
role for the perchlorate ion in transition
metal complexes. In addition, these infrared
criteria of bonding have been used to
establish that the perchlorato group, in
elongated tetragonal octahedral complexes
of the copper(ll) ion, i.e., [Cu(en) (OCIO ) ],
2
32
with long
4 Cu-O distances of 2.6 A, is still involved in weak or semi-coordination, and it
is probably in this respect that this paper has
become a Citation Classic.
“Our infrared paper was recently
5 quoted
by us in a crystallographic paper on the
structure of catena-acetato(di-2-pyridylamine)-~-perchlorato copper(ll) monohydrate which reported the crystal structure
and infrared evidence for a novel bridging
perchlorato
group involved in semi-coordi4
nation to the copper(ll) ion.”
I. Addison C C & Hathaway 81. Addition compounds of dinitrogen tetroxide and their application in preparative
inorganic chemistry. Recent aspects of the inorganic chemistry ofnitrogen: report n/a sympt~siun,held by the
Chemical Society at Cambridge on April lOth-12:h. 1957. London: Chemical Society, 1957. p. 33-43.
2.
. The vapour pressure of anhydrous copper nitrate, and its molecular weight in the
vapour state. I. Chew. Soc. 1958:3099-106.
3. Hathaway B 1. Volatile copper perchiorate. Proc. Chem. Soc. 1958:344-S.
4. Procter I M, Hathaway B I & NIcholl, P. The electronic properties and stereochemistry of the copper(I1) ion.
Part 1. Bis(ethylenediamine)copper(II) complexes. I. Chew. Soc. A 1968:1678-84.
5. Ray N, Tyagl S & Hathaway B. Catena-acetato(di-2-pyridylamine)-,~-perchloralocopperill) monohydrate.
Acta Crystallogr. Sect. 8 38:1574-7, 1982.
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